Newsbrief: Analyst firm Cowen and Company warns that, as social games giant Zynga gears up to report its second quarter earnings this week, a number of the company's key titles are about to hit negative inflection points.

Using the previous declines of FrontierVille and Mafia Wars as a case in point, Cowen analyst Doug Creutz noted that both games saw a decline in book value after they had dropped below 3.5 million daily active users -- a figure that Creutz claims has proven to be "a critical threshold" for overall social gaming users.

Worryingly for the company, eight of its top ten grossing titles, including CityVille and FarmVille, have dropped below this figure, meaning that Zynga may well soon experience notable revenue declines as a result.

Creutz also noted, "While we do think that initiatives like Zynga.com and online gambling have the potential to drive long-term upside, that view is balanced off by our belief that Zynga's core Facebook game business is likely in decline." Zynga will report its second quarter earnings on July 25.